Salts of N-acetyl cysteine and N-acetyl homocysteine are known. They are of interest as intermediates for peptide synthesis, as active pharmaceutical substances or in cosmetic preparations. For example, the sodium salt and the ammonium salt of N-acetyl-L-cysteine are used as a mucolytic agent.
The preparation of salts of N-acetyl cysteine and N-acetyl homocysteine encounters difficulties in so far as the selective N-acetylation of mercapto-.alpha.-amino acids is only possible with considerable effort.